* Aluminium exports rise slightly to 451,000 t in April
* Steel exports up 14.7 pct from March, highest since Aug 2017
* U.S. tariffs not having material impact on aluminium - analyst
By Tom Daly and Muyu Xu
BEIJING, May 8 (Reuters) - China's aluminium exports inched higher in April as U.S. import tariffs were offset by a spike in international prices due to U.S. sanctions on Rusal that encouraged Chinese firms to send more metal abroad.
Steel exports also jumped, official customs data showed on Tuesday, rising to their highest level since August last year.
The United States imposed a 25 percent duty on steel imports and a 10 percent tariff on aluminium imports, including from China, effective March 23 as U.S. President Donald Trump sought to protect U.S. metal makers.
The United States accounts for around 14 percent of Chinese aluminuim exports but only 1 percent of its steel exports.
Unwrought aluminium and aluminium product exports, including primary, alloy and semi-finished aluminium products, came in at 451,000 tonnes last month, up 0.2 percent from a revised 450,000 tonnes in March and up 4.9 percent from 430,000 tonnes in April 2017, the General Administration of Customs said on Tuesday.
April has one less day than March, so the latest increase was greater on a daily basis.
Exports of steel products, meanwhile, rose 14.7 percent to 6.48 million tonnes in April.
That compared with 5.65 million tonnes in March and 6.49 million tonnes in April 2017.
Washington imposed sanctions on Russia's Rusal, the world's second-biggest aluminium producer, on April 6, causing London Metal Exchange (LME) aluminium prices to rise 12.5 percent last month on fears of a supply shortage.
Shanghai aluminium prices climbed only 4.8 percent in April in a well supplied Chinese market, creating a price arbitrage to the LME that encouraged Chinese producers to ship more metal overseas.
"Exports are still happening, which suggests the tariff is not really having a material impact at this point," said Lachlan Shaw, a metals analyst at UBS in Melbourne.
"Certainly anecdotal reporting from within the U.S. aluminium products manufacturing sector suggests that some fabricators are just paying the tariffs to secure the required imports. So it appears that trade is holding up for now," he added.
For more details, see (Reporting by Tom Daly and Muyu Xu; additional reporting by Melanie Burton in MELBOURNE; editing by Richard Pullin)